EP0515690B1 - Fouriertransformation-massenspektrometer - Google Patents

Fouriertransformation-massenspektrometer Download PDF

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Publication number
EP0515690B1
EP0515690B1 EP91919796A EP91919796A EP0515690B1 EP 0515690 B1 EP0515690 B1 EP 0515690B1 EP 91919796 A EP91919796 A EP 91919796A EP 91919796 A EP91919796 A EP 91919796A EP 0515690 B1 EP0515690 B1 EP 0515690B1
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Prior art keywords
frequency
signal
magnetic field
resonance
ion
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French (fr)
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EP0515690A4 (en
EP0515690A1 (de
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Kazuo Nakagawa
Hiromi Yamazaki
Yasushi Takakuwa
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Nikkiso Co Ltd
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Nikkiso Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/36—Radio frequency spectrometers, e.g. Bennett-type spectrometers, Redhead-type spectrometers
    • H01J49/38—Omegatrons ; using ion cyclotron resonance

Definitions

  • the present invention relates to a process for measuring an amount of a target component in a mixed sample gas as described in the preamble of claim 1 as well as to a Fourier transform mass spectrometer according to the preamble of claim 3. More particularly, the present invention relates to a Fourier transform mass spectrometer suitable generally for concentration analysis of any mixed gas samples including a so-called process analysis for process stream in chemical plants, a so-called medical gas analysis for carrying out analysis of metabolic functions and anesthetic states or monitoring them by analyzing respiratory gases or inhalation gases from or into the living body, a so-called evolved gases analysis for analyzing evolved gases for estimating the state of a surface of a semiconductor, a catalyst or the like or the progress of a reaction thereof from a gaseous component eliminating therefrom by heating them, or so on.
  • a Fourier transform mass spectrometer suitable generally for concentration analysis of any mixed gas samples including a so-called process analysis for process stream in chemical plants, a so-called medical gas analysis for carrying out analysis of metabolic functions and
  • a transmission unit supplying high-frequency electric field, mounted to the Fourier transform mass spectrometer, for forming an electric field for ionizing a gaseous sample has the function for sweeping a whole region of resonant frequency corresponding to a whole region of mass to be measured at a high speed so as to excite all kinds of ions.
  • the conventional transmission unit excites ions which are not required for excitement, so that voltage of a signal to be induced into a receiving electrode of an analyzing cell amounts to a total sum of outputs caused by resonance from all the ions containing the unnecessary ions.
  • an intensity of an ion cyclotron resonance signal of the ion to be induced is so restricted as not to exceed a dynamic range of analog-digital conversion, so that the ion to be measured cannot be excited until the ion cyclotron resonance signal of the ion to be measured becomes to a sufficiently high level.
  • the conventional Fourier transform mass sepctrometer presents the problem that there is no correlation between a static magnetic field and the frequency to be irradiated.
  • a permanent magnet, an electric magnet or the like is employed, not a super-conductive magnet, application of the static magnetic field for a long term causes the irradiating frequency to deviate from the resonant magnetic field, thereby making the desired ion difficult to be excited.
  • a process and an apparatus for measuring an amount of a target component in a mixed sample gas according to the preambles of claim 1 and 3, respectively, is known from US-A-3 937 955.
  • the spectrometer comprises a sample cell arranged in a D.C. polarizing magnetic field produced by an electromagnet.
  • a radio frequency signal is supplied to a transmitter coil associated with the sample cell and to a phase detector. Resonance signals emanating from the sample are fed to the phase detector.
  • An audio frequency signal derived from the resonance signal by the phase detector is used for analyzing.
  • a control signal is derived from a portion of the transient audio frequency resonance signal.
  • the phase of a component of a selective resonant line selected for the control is compared with an audio frequency reference signal corresponding to the selected resonant line.
  • a D.C. control signal is obtained which indicates any tendencies for the gyromagnetic ratio of polarizing magnetic field intensity to the R.F. frequency of the output signal of the R.F. transmitter to depart from a predetermined ratio.
  • the control signal is used to correct either the intensity of the polarizing magnetic field or the frequency of the R.F. signal.
  • This method that is a continuous controlling method performed by negative feedback of an analog D.C. signal cannot be applied to Fourier transform ion cyclotron resonance spectroscopy.
  • the object of the present invention is to provide a process for measuring an amount of a target component in a mixed sample gas and a Fourier transform mass spectrometer which are capable of making a ratio of a strength of the static magnetic field to the irradiating frequency constant so that a particular kind of ion to be measured can be excited until a resonant signal of the ion becomes sufficiently high and mass analysis of said ion can be performed in a stable manner for a long term.
  • the ion cyclotron resonance frequency for a residual component left present in high vacuum circumstances, such as hydrogen or nitrogen, is measured in advance, and the ion cyclotron resonance frequency measured is stored as a reference frequency.
  • an ion cyclotron resonance frequency of a particular gaseous component that does not interfere with the object of measurement, such as argon or the like is measured in advance and this ion cyclotron resonance frequency is stored as a reference frequency.
  • the mass number of the ion at the time of ionization of the particular component serving as the object of measurement is input, and the ion cyclotron resonance frequency of the particular ion is computed and determined on the basis of the mass number of the particular ion and the reference frequency stored in advance in the memory.
  • the resulting ion cyclotron resonance frequency is then stored.
  • the sample gas as the object of measurement is introduced into the high vacuum cell of which the pressure has been reduced to a high degree of vacuum.
  • the static magnetic field caused to occur by means of magnetic field occurring means such as the permanent magnet or the electric magnet.
  • high frequency is applied to the pair of the irradiating electrodes disposed within the high vacuum cell from the high-frequency transmitting means, thereby applying the high-frequency electric field to the ions present in the high vacuum cell.
  • the application of the high-frequency electric field may be made in a manner as will be described hereinafter.
  • the ion cyclotron resonance frequency stored in the memory is read out by the clock pulse generated from the clock pulse generator, and it is subjected to D/A conversion, followed by application to the pair of the irradiating electrodes. This allows the ions as the object of measurement to be applied to by the static magnetic field from the permanent magnet or the electric magnet as well as the high-frequency electric field of the particular frequency, thereby inducing an ion cyclotron resonance signal of the particular ion.
  • the ion cyclotron resonance signal induced is then detected as a high-frequency decaying electric signal.
  • the high-frequency decaying electric signal is converted into a digital signal by means a high-speed A/D converter.
  • the high-frequency decaying electric signal is called the time-domain signal.
  • the high-frequency decaying electric signal in the digital form is converted into the frequency-domain signal by the technique of Fourier transformation.
  • the frequency-domain signal corresponds to a mass spectrum and the unit of the signal frequency can be readily converted to thereby give a usual mass number because there is the relationship between the frequency and the mass number as shown in the formula (2) as will be described hereinafter.
  • the irradiating frequency close to the ion cyclotron resonance frequency of the particular ion to be measured is applied to the pair of the irradiating electrodes, so that the particular ion to be measured can be excited to such a sufficiently high level as being measurable within a limited dynamic range in converting the detected high-frequency decaying signal into the corresponding digital signal.
  • the Fourier transform mass spectrometer can continuously detect the particular ion as the object of measurement within the sample gas in a continuous manner by supplying the sample gas to the high vacuum cell continiously or periodically.
  • the drift of the static magnetic field is detected as a deviation in the ion cyclotron resonance frequency, and the frequency of the reading clock pulse corresponding to the varied ion cyclotron resonance frequency is determined, thereby feeding back the frequency deviation to the clock pulse generator.
  • the clock pulse generator changes the frequency of the reading clock pulse according to the feedback signal.
  • the wave form for irradiation frequency stored in the memory is read out by the clock pulse having its frequency changed and subjecting the resulting ion cyclotron resonance frequency to D/A conversion, followed by applying the resulting signal to the pair of the irradiating electrodes.
  • the Fourier transform mass spectrometer can detect the drift of the static magnetic field as a deviation in the ion cyclotron resonance frequency, even if the static magnetic field would change for a long term, change the frequency of the reading clock pulse in accordance with the changes in the ion cyclotron resonance frequency, convert the read high frequency wave form to analog signal, and apply the resulting analog signal to the pair of the irradiating electrodes, so that the Fourier transform mass spectrometer can be arranged so as to hold the ratio of the static magnetic field to the frequency of the high-frequency electric field constant relative to a change in the temperature of the environment encountered with the room where the Fourier transform mass spectrometer is disposed or with the spectrometer.
  • Fig. 1 is a block diagram showing an spectrometer according to an embodiment of the present invention.
  • Fig. 2 is a schematic representation describing a cubic cell.
  • Fig. 3 is a block diagram showing a generator for generating a signal to be transmitted, mounted to the Fourier transform mass spectrometer according to the present invention.
  • Fig. 4 is a diagram showing wave forms of signals to be transmitted from each section of the Fourier transform mass spectrometer according to the embodiment of the present invention.
  • a Fourier transform mass spectrometer 1 as shown in Fig. 1 comprises a high vacuum cell 2 into which a sample gas is introduced and ionized, magnetic field generating means 5 using a permanent magnet 3 for forming static magnetic field for the sample gas within the high vacuum cell 2, a high frequency source 7 for providing the particular ions present in the high vacuum cell 2 as the object of measurement with high-frequency electric field from a plurality of fixed frequencies for exciting ion cyclotron resonance, detection means 8 for detecting the ion cyclotron resonance excited within the high vacuum cell 2 as a high-frequency decaying signal, operation controlling means 9 for controlling the ratio of the static magnetic field to the frequency at a constant by converting the high-frequency decaying signal to a frequency-domain signal determining a drift of the applied magnetic field for a long term by the magnetic field generating means 5 as a deviation in an ion cyclotron resonance frequency for the particular ion, and subjecting the extent of the deviation in the ion cyclotron resonance frequency to feedback to the high frequency
  • the long term drift of the magnetic field applied from the magnetic field generating means 5 can be determined as the change of the ion cyclotron resonance frequency for the particular ion for reasons as will be described hereinafter.
  • the cyclotron resonance frequency of the ion is determined in proportion to the static magnetic field substantially. Hence, if the field applied varies for a long term, the ion cyclotron resonance frequency varies, too, in proportion to the long term variation in the magnetic field applied. Therefore, the long-term variation of the magnetic field applied for a certain period of time can be determined by continuously monitoring the ion cyclotron resonance frequency of the particular ion.
  • the high vacuum cell 2 is protected with a very high vacuum chamber 13 and accommodated in a thermostat vessel, although not shown.
  • the high vacuum cell 2 is disposed in the very high vacuum chamber 13 and the inside of the very high vacuum chamber 13 is maintained at a high vacuum level as in the high vacuum cell 2. Further, by accommodating them in the thermostat vessel, the inside of the high vacuum cell 2 is always maintained at a constant temperature.
  • the high vacuum cell 2 there may be employed a hexahedral or cubic cell comprising three pairs of electrodes one of which is disposed in the direction perpendicular to the direction of magnetic field generated by the magnetic field generating means 5, two pairs of electrodes, one pair for irradiating and the other for receiver, disposed in the position parallel to the magnetic field and perpendicular to each other.
  • Such a hexahedral or cubic cell may include, for example, conventional one as described, for example, in R. T. McIver Jr.: Rev. Sci. Instrum., 41, 555 (1970); M. B. Comisarow: "Cubic Trapped Ion Cell For Ion Cyclotron Resonance"; Int. J. Mass Spect. Ion Phys., 37(1981), p. 251, and the like.
  • a pair of the electrodes P and P' which makes the hexahedral cell in such a manner as to be perpendicular to the direction of the magnetic field generated by the magnetic field generating means 5, are provided with a slight strength of positive potential, for example, from 1V to 2V, in order to prevent the ions drift along the direction of the magnetic field, within the high vacuum cell 2.
  • the irradiating electrodes T and T' are interposed between the pair of the electrodes P and P' so as to face them along the direction of the magnetic field, thereby allowing the high-frequency signal for exciting the ions generated in the hexahedral or cubic cell to cause the cyclotron resonance for a period of time, for example, as short as 0.1 ms to 10 ms.
  • the receiving electrodes R and R' are disposed so as to face along the direction of the magnetic field and to be perpendicular to the electrodes P and P' as well as the irradiating electrodes T and T', thereby receiving the voltage of the high-frequency signal to be induced by the resonance.
  • the thermostat vessel is so arranged as to allow the magnetic field generating means 5 to maintain changes in its temperatures within, for example, 0.1 °C or less, relative to the ambient temperature, thereby alleviating the drift of the magnetic field due to the changes of the ambient temperatures.
  • the ambient temperature may change in the range of from 10°C to 30 °C or more over the length of several months.
  • the permanent magnet 3 to be employed as the magnetic field generating means 5 comprises a pair of magnetic pole pieces 3a and 3b, each being disposed so as to face the high vacuum cell 2.
  • the use of the permanent magnet 3 offers one of the features for the present invention.
  • the magnetic field caused by the permanent magnet 3 and the electric magnet changes due to the influence of the ambient temperature as well as that a coefficient of temperature may be from approximately -2 x 10 -4 / °C for the electric magnet and it may range from -5 x 10 -4 to -6 x 10 -3 /°C for a permanent magnet made of a rare earth and iron.
  • a coefficient of temperature may be from approximately -2 x 10 -4 / °C for the electric magnet and it may range from -5 x 10 -4 to -6 x 10 -3 /°C for a permanent magnet made of a rare earth and iron.
  • thermoperm compensation by means of a special magnetic shunt steel, what is called thermoperm, may appropriately be adopted as means for compensating the coefficient of temperature.
  • This compensation can improve the coefficient of temperature to degrees higher by several times.
  • a neodimium-iron-boron type bond magnet Nd 2 Fe 14 B
  • Nd 2 Fe 14 B has an improved coefficient of temperature up to ⁇ 1 x 10 -3 / °C at the present time.
  • the high frequency source 7 comprises a clock pulse generator 17 for generating clock pulse signals having a predetermined cycle, a high frequency generator 15 as will be described hereinafter in more detail, and a high frequency transmitter 16 for transmitting the high frequency generated by the high frequency generator 15 to the irradiating electrodes.
  • the detection means 8 comprises a pre-amplifier 20, a high-frequency amplifier 21, a low-pass filter 22 and a high-speed processable A/D converter 23.
  • the pre-amplifier 20 is adapted to amplify the ion cyclotron resonance frequency induced by the receiving electrode R and R' disposed in the high vacuum cell 2 and transmit the amplified ion cyclotron resonance signal to the high-frequency amplifier 21.
  • the pre-amplifier 20 there may be employed a so-called narrow band-width amplifier having a narrow range of pass band frequencies relative to the central frequency so as to allow the ion cyclotron resonance frequency for the particular ion as the object of analysis to be amplified selectively.
  • the high-frequency amplifier 21 is adapted to subject the ion cyclotron resonance signal amplified in a narrow pass band and a reference signal of frequency fo entered separately to mixed processing, thereby converting the ion cyclotron resonance signal into a low-frequency signal, that is, difference frequency signal between the resonance and reference frequencies and transmitting the low-frequency signal to the low-pass filter 22.
  • the conversion of the frequencies is carried out by holding information on the amplification and the phase of signal waves and converting only the frequency into the difference frequency between the resonance and the reference frequencies from the reference frequency.
  • the reference frequency fo is preferably set to be higher than the ion cyclotron resonance frequency.
  • the low-pass filter 22 is adapted so as to eliminate folding over signals at the time of the A/D conversion by the A/D converter 23, and the cut off frequency is set in advance to be lower by a half times, or less, comparing with the clock frequency of the A/D converter 23.
  • the A/D converter 23 converts the resonance signals, which are eliminated unnecessary frequency signals and amplified to the signal level to such an extent as being convertible, to the digital signals corresponding to the resonance signals, followed by generating the resulting digital signal to the operation controlling means 9.
  • the operation controlling means 9 comprises a computer 27 for implementing control over the whole system, a memory 28 as storage means, an output unit 29, and an interface 30 for controlling the A/D converter 23 as well as receiving outputs from the A/D converter at a high speed and transmitting a control signal from the computer 27 to the source 6 for highly stabilized direct current and to the high-frequency generator 15.
  • the high-frequency generator 15 will now be described in more detail with reference to Fig. 3.
  • the high-frequency generator 15 comprises an input latch unit 41 for latching the digital signal entered from the operation controlling means 9, the digital signal being data in the form of a high-frequency wave necessary for exciting the ion cyclotron computed by the operation controlling means 9 on the basis of the formula (1) or (2) as will be described hereinafter, a high-speed memory 42 for storing the data signal in the high-frequency wave form entered from the input latch unit 41, a D/A converter 43 for converting a data signal from the high-speed memory 42 into analog signals, an output amplifier 44 for amplifying the output from the D/A converter 43 and generating the signal as a high-frequency output signal, an output gate 45 for switching the high-frequency output signal generated from the output amplifier 44 and sending the signal to the high-frequency transmitter 16, a latch control unit 46 for implementing latch control of the input latch unit 41, a memory controlling unit 47 for implementing read-write control and address control of the high-speed memory 42, a D/A conversion controlling unit 48 for controlling the conversion for the D/A converter 43 by reading the
  • the output control unit 49 contains a gate circuit for controlling an operational clock signal for the high-speed memory 42 and the D/A converter 43 in response to input of the clock signal from the clock pulse generator 17.
  • the high-frequency output signal to be generated from a terminal for the high-frequency output signal is generated to the high vacuum cell 2 through the high-frequency transmitter 16 as an excited high-frequency pulse required for causing the ion cyclotron resonance.
  • ⁇ B x e/m Where e is a charge of ion.
  • the static magnetic field B can be established by measuring the resonance frequency of the particular component and computing the formula (2) above on the basis of the resonance frequency measured.
  • the resonance frequency of a nitrogen molecule, a hydrogen molecule and the like remaining in high vacuum atmosphere can be measured with ease.
  • the mass number (m/z) is determined as a physical constant on the basis of the kind of ions and it is not difficult to give the mass number with high accuracy as high as five to seven digits as effective number because the value ⁇ o is the frequency of resonance to be measured.
  • a signal to be transmitted in a wave form can be given by the formula (4) as follows: where ⁇ i is (m/z) o /(m/z) i x ⁇ o
  • the frequency ⁇ o of resonance for each of nitrogen or hydrogen in advance as a reference frequency and store it, for instance, in the storage 28 of the operation controlling means 9.
  • the frequency of resonance for each of nitrogen or hydrogen may be measured, for instance, by reducing the pressure in the high vacuum cell to a high vacuum level without supplying the sample gas thereinto, ionizing the remaining nitrogen or hydrogen, and inducing the ion cyclotron resonance by means of the static magnetic field and the high-frequency electric field.
  • the mass number (m/z) of the ion as the object of measurement present in the sample gas is inputted through the keyboard 11.
  • the operation controlling unit 9 reads out the reference frequency stored in the storage 28, computing the frequency of the ion as the object of measurement in accordance with the formula (3) above, and storing the resulting frequency in the high-speed memory 42.
  • the mass numbers of each kinds of ion is inputted through the keyboard 11, the wave form is computed in accordance with the formulas (4) and (5), followed by storing the resultant united wave form in the high-speed memory 42.
  • the sample gas is first introduced into the high vacuum cell, which has been exhausted to a high vacuum extent.
  • the sample gas is then ionized upon irradiation of electron beams or the like upon the sample gas in the high vacuum cell.
  • the static magnetic field generated by the permanent magnet To the ion generated is applied the static magnetic field generated by the permanent magnet. In measuring, the high-frequency electric field is first applied to the resulting ion.
  • the application of the high-frequency electric field may be implemented in the manner as will be described hereinafter.
  • the computer 27 is adapted to compute the waveform of the transmitting signal with respect to the time t in accordance with the formula (3) above or the formulas (4) and (5) above and the resulting signal is stored in the high-speed memory 42 through the input latch unit 41.
  • the data signal computed with accuracy in a 12-bit is transmitted on each 8 bits to a bus line so that the data signal is transmitted twice as a high order byte and a low order byte.
  • each byte is temporarily stored (latched) and stored as two-byte data in the high-speed memory 42.
  • control signal for controlling the operation of each of these units and portions is generated from the computer 27.
  • the output from the input latch unit 41 is first brought into a state of high impedance, thereby isolating the bus line from the high-speed memory 42.
  • the memory controlling unit 47 brings the high-speed memory 42 in a read state and an address of the reading data is specified.
  • the computer 27 generates an output gate signal specified separately to the output controlling unit 49 which in turn decodes a code indicative of the start of measurement in the output gate signal. As the signal decoded is generated to the output gate 45, the output gate 45 is brought into an ON state.
  • the computer 27 generates the control signal to the memory controlling unit 47, thereby allowing the data signal stored in the high-speed memory 42 to be read out by means of the clock pulse having a constant frequency to be generated from the clock pulse generator 17, and converting the resulting signal into the analog signal by the D/A converter 43, followed by the generation of the resultant analog signal to the high-frequency transmitter 16.
  • the high-frequency transmitter 16 implements pulse modulation in response to the analog signal and supplies a two-phase high-frequency pulse of electric power strong enough to excite and send to the irradiating electrodes of the high vacuum cell 2.
  • the Fourier transform mass spectrometer 1 for analyzing gases applies to the mass number of 200 [amu] or lower and employs a permanent magnet of approximately 0.6 [T] for the static magnetic field.
  • a pulse of 16 MHz is employed for clock because the resonance frequency is approximately 4.8 kHz for hydrogen, approximately 345 kHz for nitrogen, and approximately 75.5 kHz for 129 Xe.
  • a D/A converter and a random-access memory, each being capable of being driven at this clock frequency can currently be commercially available.
  • the transmission time is set to 1 ms, the number of data to be stored is 16,000 and a memory size is 24,000 bytes.
  • Fig. 4 shows a typical relationship between the applied voltage of each electrode of the high vacuum cell 2 in a cycle of analysis and the signals induced. As shown in Fig. 4,
  • the high-frequency electric field having a fixed frequency is applied to the particular ion to be measured within the sample gas in the manner as described hereinabove, so that this embodiment can offer the feature that the ion to be measured can be excited to a great extent within the dynamic range of the D/A converter. Further, this embodiment has the great feature that the clock frequency for reading the transmitting waveform signal can be changed in accordance with the drift in the static magnetic field in repeating the cycles for excitement and measurement in the manner as described hereinabove, thereby holding the ratio of the magnetic field to the frequency in a constant fashion.
  • the transmitting output wave form for exciting resonance is stored in the high-speed memory 42, so that the output frequency can be changed so as to become proportional to the frequency of the reading clock.
  • the measurement can be continued while retaining the ratio of the magnetic field to the frequency at a substantially constant level.
  • the clock pulse generator 17 having the configuration as described hereinabove can readily be realized, for example, by taking advantage of a known frequency synthesizing technique or the like.
  • the ion cyclotron resonance frequency of the particular ion is detected by the receiving electrodes of the high vacuum cell 2 and generated to the pre-amplifier 20 as high-frequency signal voltage.
  • the pre-amplifier 20 is not required to amplify and transmit all the high-frequency signal voltage of all the ions on the basis of the whole components constituting the sample gas and it is satisfactory to use the narrow-band amplifier having response to the resonance signal corresponding to the particular ion.
  • this arrangement can offer the features as follows:
  • the high-frequency amplifier 21 receiving the output from the pre-amplifier 20 implements the mixed processing with the reference signal fo after amplification of the resonance signal and then generates the low-frequency signal of the difference frequency to the low-pass filter 22.
  • the low-pass filter 22 is adapted to eliminate the folding over signals caused to occur at the time of conversion by the A/D converter 23, and the cutoff frequency is set in advance to become lower by half times or less, comparing with the clock frequency of the A/D converter 23.
  • the resonance signal from which the band of the unnecessary frequency has been eliminated and which has been amplified to the signal level suitable for the A/D converter 23 is then converted into the digital signal by the A/D converter 23 and transmitted to the computer 27 via the high-speed interface 30, followed by storing in the storage 28 as time-region data.
  • the time-region data is subjected to Fourier conversion at a high speed by the computer 27, thereby converting the time-domain data into a frequency-domain data, that is, a mass spectrum.
  • the high-frequency sources for measurement and the amplifiers for amplifying the narrow-band signals may be added.
  • This arrangement can be implemented with ease by taking advantage of a plug-in unit type.
  • a single frequency synthesizer may be disposed, in place of plugging in the high-frequency source units corresponding to the respective components to be measured, so as to be shifted one after another during the period of time during which the ions are being excited.
  • the permanent magnet is employed as the source of forming the static magnetic field in the aforesaid embodiment
  • the electric magnet can also be employed in place of the permanent magnet and it can demonstrate the similar technical effects.

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Claims (5)

  1. Verfahren zum Messen der Menge einer Zielkomponente in einem Probengasgemisch, das folgendes umfasst:
    Anlegen eines hochfrequenten elektrischen Felds an ein Ion, das im Hochvakuum aus dem Probengasgemisch ionisiert wurde und in einem durch einen Permanentmagnet oder einen Elektromagnet erzeugten statischen Magnetfeld vorhanden ist, um Ionenzyklotronresonanz zu induzieren;
    Erfassen eines Resonanzsignals durch die Ionenzyklotronresonanz;
    Umsetzen des Resonanzsignals in ein digitales Signal in der Zeitdomäne und
    Umsetzen des digitalen Signals in der Zeitdomäne in ein Signal in der Frequenzdomäne;
    dadurch gekennzeichnet, dass
    vorab ein Signalverlauf, der auf Grundlage der Winkelfrequenz bei Resonanz des Zielions erstellt wurde, in Form einer Abfolge abgespeichert wird, die eine Anzahl digitaler Daten in der Zeitdomäne umfasst;
    die gespeicherten digitalen Daten einzeln mit derselben Abfolge mit einem Intervall ausgelesen werden, das durch die Frequenz eines Taktimpulses bestimmt ist;
    die ausgelesenen digitalen Daten in einen analogen Signalverlauf umgesetzt werden, der dazu verwendet wird, das hochfrequente elektrische Feld zu erzeugen; und
    eine Langzeitdrift des statischen Magnetfelds als Änderung des Werts der Ionenzyklotronresonanz-Frequenz einer speziellen Komponente im Probengasgemisch erfasst wird, damit die Frequenz des Taktimpulses entsprechend der Änderung variiert wird, um dadurch das Verhältnis aus der Stärke des statischen Magnetfelds zur Frequenz, bei der das Zielion in Resonanz sein kann, konstant zu halten.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass dann, wenn jeweilige Mengen mehrerer Komponenten im Probengasgemisch gemessen werden, der Signalverlauf dadurch erstellt wird, dass die aus den jeweiligen Frequenzen, bei denen die Zielionen der entsprechenden Komponenten in Resonanz stehen, berechneten Elementsignalverläufe überlagert werden.
  3. Fouriertransformation-Massenspektrometer (1) mit:
    einer Hochvakuumzelle (2) mit einem Paar Bestrahlungselektroden (T, T');
    wobei die Bestrahlungselektroden (T, T') jeweilige plattenförmige, parallel zueinander angeordnete Flächen zur Bestrahlung aufweisen;
    einer Speiseeinrichtung zum Einspeisen von Molekülen eines Probengasgemisches einschließlich Zielkomponenten in die Hochvakuumzelle (2);
    einem Elektronenstrahlgenerator zum Strahlen eines Elektronenstrahls auf die in die Hochvakuumzelle (2) eingespeisten Moleküle des Probengasgemisches zum Ionisieren der Moleküle des Probengasgemisches, um Ionen der jeweiligen Zielkomponenten zu erhalten;
    einer Magnetfeld-Erzeugungseinrichtung (3) zum Erzeugen eines statischen Magnetfelds in einer Richtung parallel zu den jeweiligen Flächen der Bestrahlungselektrode (T, T') in der Hochvakuumzelle (2);
    einem Hochfrequenzgenerator (15), der mehrere analoge Signalverläufe mit hohen Frequenzen erzeugen kann;
    einem Hochfrequenzsender (16), der mit dem Hochfrequenzgenerator (15) und der Hochvakuumzelle (2) verbunden ist und die analogen Signalverläufe zu den Bestrahlungselektroden (T, T') liefert, um dadurch Ionenzyklotronresonanz zu induzieren;
    einer Erfassungseinrichtung (8), die mit der Zelle verbunden ist, um ein Resonanzsignal aufgrund von Ionenzyklotronresonanz zu erfassen und um das Resonanzsignal in ein digitales Signal in der Zeitdomäne umzusetzen;
    einer Betriebssteuerungseinrichtung (9), die mit der Erfassungseinrichtung (8) verbunden ist, um das digitale Signal in der Zeitdomäne in ein Signal in der Frequenzdomäne umzusetzen;
    einer mit der Betriebssteuerungseinrichtung (9) verbundenen Tastatur (11), mittels der die Zielkomponenten eingegeben werden; und
    einer mit der Betriebssteuerungseinrichtung (9) verbundenen Anzeige (10);
    dadurch gekennzeichnet, dass
    der Hochfrequenzgenerator (15) einen mit der Betriebssteuerungseinrichtung (9) verbundenen Hochgeschwindigkeitsspeicher (42) und einen mit diesem Hochfrequenzspeicher (42) und dem Hochfrequenzsender (16) verbundenen D/A-Wandler (43) zum Umwandeln digitaler, vom Hochgeschwindigkeitsspeicher (42) ausgegebener Daten in einen analogen Signalverlauf aufweist;
    ein Taktimpulsgenerator (17), der die Frequenz des von ihm erzeugten Taktimpulses variieren kann, mit dem Hochfrequenzgenerator (15) und der Betriebssteuerungseinrichtung (9) verbunden ist; und
    die Betriebssteuerungseinrichtung (9) ebenfalls mit dem Hochfrequenzgenerator (15) verbunden ist und folgendes aufweist:
    einen Speicher (28) zum Speichern einer Bezugswinkelfrequenz (
    Figure 00360001
    ), die durch Messen der Resonanzwinkelfrequenz einer speziellen Komponente im Probengasgemisch erhalten wurde; und
    einen Prozessor (27), der mit dem Speicher (28) verbunden ist,
    um Frequenzen zu berechnen, für die Resonanz der jeweiligen Ionen der entsprechenden Zielkomponenten existiert, zum Erstellen eines Signalverlaufs aus den Frequenzen und zum Übertragen des Signalverlaufs an den Hochgeschwindigkeitsspeicher (42), damit er in einer Abfolge gespeichert wird, die eine Vielzahl digitaler Daten in der Zeitdomäne umfasst;
    um den Hochgeschwindigkeitsspeicher (42) in regelmäßigen, durch die Frequenz des Taktimpulses bestimmten Intervallen dazu anzuweisen, die gespeicherten digitalen Daten einzeln mit derselben Abfolge an den D/A-Wandler (43) zu liefern; und
    um auf eine Änderung des Werts der Resonanzwinkelfrequenz der speziellen Komponente dadurch zu achten, dass er den Wert mit der Bezugswinkelfrequenz ( ) vergleicht und den Taktimpulsgenerator (17) abhängig von der Änderung dazu anweist, die Frequenz des Taktimpulses zu variieren.
  4. Fouriertransformation-Massenspektrometer (1) nach Anspruch 3, dadurch gekennzeichnet, dass die Hochvakuumzelle (2) eine sechsflächige oder kubische Zelle ist, die ferner ein Paar Elektroden (P, P'), die so angeordnet sind, dass sie rechtwinklig zur Richtung des durch die Magnetfeld-Erzeugungseinrichtung (5) erzeugten Magnetfelds stehen, und ein Paar Empfangselektroden (R, R') aufweist.
  5. Fouriertransformation-Massenspektrometer (1) nach Anspruch 4, dadurch gekennzeichnet, dass die Erfassungseinrichtung (8) einen Vorverstärker (20) zum Verstärken des durch die Empfangselektroden (R, R') induzierten Resonanzsignals mit der Ionenzyklotronresonanz-Frequenz sowie einen Hochfrequenzverstärker (21), um das vorverstärkte Resonanzsignal und ein Bezugssignal einer Frequenz (fo), die beide gesondert eingegeben werden, einer Mischverarbeitung zu unterziehen und das vorverstärkte Resonanzsignal in ein niederfrequentes Signal mit der Differenzfrequenz zwischen der Resonanzfrequenz und der Bezugsfrequenz (fo) umzusetzen, aufweist.
EP91919796A 1990-11-19 1991-11-19 Fouriertransformation-massenspektrometer Expired - Lifetime EP0515690B1 (de)

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PCT/JP1991/001581 WO1992009097A1 (en) 1990-11-19 1991-11-19 Fourier-transform mass spectrometer

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DE69131447D1 (de) 1999-08-19
US5264697A (en) 1993-11-23
WO1992009097A1 (en) 1992-05-29
JP3334878B2 (ja) 2002-10-15
EP0515690A4 (en) 1993-05-05
EP0515690A1 (de) 1992-12-02

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